Multiple Queries are not working
Multiple Queries are not working on my linode server, single queries works fine, unable to understand the issue, previously everything was working fine.
When it comes to troubleshooting database performance issues, the best tool I know is mysqltuner. We have a guide on how to get set up using this tool: How to Optimize MySQL Performance Using MySQLTuner.
Aside from that, I would also suggest reviewing the service logs for your database. If you haven't done that before, this Community Questions post should help: How do I check my server's log files?. Often, the service logs will provide details at the database level as to what might be happening.