Play v10, v11 or v12?

Dear ALL, I have done latest setup yesterday erpnext using

My guest is ovb ubuntu 18.04 lts with 2vpu and 8gb ram inside wins 8.1 64.

I found that front end is ok but backend kind of slow. Alot of time, worker is dead, mysql / mariadb is full of connections complaining about too many files opened.

Is there a way to setup python 2 stable version for stable assessment. Is v11 consider to be stable or just v10?

Is erpnext v11 the last stable version for python2? or is it v10? I found v12 is really not production ready while testing it.

V12 also works with python 2.7 but python 3 is recommended.