Tier2G to tier4 student

[KEY2015]

Hii Gurus,

I have been in UK for 7years and currently in tier2G dependant for last 3months.My spouse tier 2 sponsor is in trouble now.So we want to be safe before something happens. So I would like to switch to tier 4student visa.
1)is it possible to switch to tier 4 student visa in country?
2)if its not possible,if i apply from outside of the country,my 7years continuity will come to on end since its going to be a another entry clearance?
3)If not,how long i can take to apply for visa outside of the country for the continuity not to be missed?
(Note: i was a tier 4 student before switched into tier 2dependant)
Please Advise that would really helpful to me.Many thanks

[KEY2015]

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