Upgrading solr failing all the rules

Hi Team,

I upgraded Solr 3.5 to 8.11.1 , we have also some custom code in solr , so i upgraded the solr version, convert schema and config file as per new version and place the jar file of custom code. but after upgrading it , all rules are failing.

in Solr Admin if any query have OR then it give below error 

java.lang.NullPointerException at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:656) at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:443) at org.apache.solr.search.SolrIndexSearcher.buildAndRunCollectorChain(SolrIndexSearcher.java:211) at org.apache.solr.search.SolrIndexSearcher.getDocListNC(SolrIndexSearcher.java:1622) at org.apache.solr.search.SolrIndexSearcher.getDocListC(SolrIndexSearcher.java:1439) at org.apache.solr.search.SolrIndexSearcher.search(SolrIndexSearcher.java:596) at org.apache.solr.handler.component.QueryComponent.doProcessUngroupedSearch(QueryComponent.java:1511) at org.apache.solr.handler.component.QueryComponent.process(QueryComponent.java:390) at com.spgi.highlighter.solr.SpgiQueryComponent.process(SpgiQueryComponent.java:25) at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:376) at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:216) at org.apache.solr.core.SolrCore.execute(SolrCore.java:2637) at org.apache.solr.servlet.HttpSolrCall.execute(HttpSolrCall.java:794) at org.apache.solr.servlet.HttpSolrCall.call(HttpSolrCall.java:567) at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:427) at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:357) at org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:201) at org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1601) at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:548) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:600) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:235) at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1624) at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:233) at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1434) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:188) at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:501) at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1594) at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:186) at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1349) at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141) at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:191) at org.eclipse.jetty.server.handler.InetAccessHandler.handle(InetAccessHandler.java:177) at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:146) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127) at org.eclipse.jetty.rewrite.handler.RewriteHandler.handle(RewriteHandler.java:322) at org.eclipse.jetty.server.handler.gzip.GzipHandler.handle(GzipHandler.java:763) at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127) at org.eclipse.jetty.server.Server.handle(Server.java:516) at org.eclipse.jetty.server.HttpChannel.lambda$handle$1(HttpChannel.java:400) at org.eclipse.jetty.server.HttpChannel.dispatch(HttpChannel.java:645) at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:392) at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:277) at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:311) at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105) at org.eclipse.jetty.io.ChannelEndPoint$1.run(ChannelEndPoint.java:104) at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:338) at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:315) at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:173) at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:131) at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:409) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:883) at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1034) at java.lang.Thread.run(Thread.java:750) 

Please help me for resolving the issue. also if i required to prepare the custom code jar file which is created based on 8.5 version then provide me how to set up and debug the solr project as i am new in java so it's very help full if you provide document for prerequisist and it's setup document.

another thing in code we are using solrNet client for indexing and searching. indexing working properly but searching is not working , so is solrNet support the 8.11.1 version?