Switch from Tier 5 to Spouse visa in Country

Hi
I am posting this question on behalf of my friend who is Canadian national living and working in UK under Tier 5 worker
He is here in this country from last 5 years (did his bachelors and masters degree) then returned back and re-entered as Tier 5 worker.
Now he wants to get married with a British National.
Questions are:

1: Can he switch in country from Tier 5 to spouse visa ?

2: He is working and drawing over 20k/annum, while his (would be) partner is a full time student in the UK.
If they can switch in country then they meet £18600 requirement ? or its mandatory for the UK citizen to earn £18600/annum in order to sponsor a non UK partner ?

any help would be greatly appreciated
Regards

Hi all

32 views, and a week gone but no reply so far

Request to all seniors, moderators Please help
Regards

1. Switching is possible (D-LTRP).

2. Income may be from either/both partners (1(c)).