Switch from Tier 2 ICT to Tier 4 Student without cooling off period?

Hi,

Am in ICT Tier2 Visa and started in Aug-2015, Am finishing my five years by Jul 2020. i would like to stay back and continue here. I knew ICT Tier 2 have Cooling off period for 12 months hence i am seeing options to continue.
I wanted to go as Student Visa (Tier 4) for Sep-2020, To apply this do i have to go back to home country or i can apply here from UK before my current Visa expires by July-2020 to get the Admission into university and continue without moving out from UK? Will my cooling off period will make any issue here?

Also please let me know as we are getting Post Study work permit (PSW Visa) after study now from 2021, Am i eligible for that or I have to serve my ICT Tier 2 cooling off period once my study Visa over. Could you please clarify on this.
Am i eligible to get any Tier-2 General sponsor for myself to do job in UK after my 2 year course over, In this case any issue with cooling off period will be there?

My spouse now working as dependant hope she can continue as Tier 4 dependant for her job and can i change her visa from UK inside as Tier-4 dependant. Could you please clarify me on these queries.

Thanks in Advance.