You may offer your qaza salahs anytime except three prohibited times. You may offer the qaza of Fajr after Isha salah as well. If you can offer the qaza of two hundred salahs in one time then you may do so. You can offer qaza salah in the time of Zuhr, Asar, Maghrib and Isha time as well. You may also offer the qaza of 100 salahs in one day. There is no qaza of sunnah. You only have to make the qaza of fardh and witr salah. You should note down the number of the qaza salah which you offer in a notebook with month and date so that you could know the exact number of salah which you have offered and which are left.
It is not lawful to offer any salah during three times: (1) when the sun is rising, (2) at the time of setting the sun and (3) in the noon time when the sun is on head.
Allah knows Best!
Darul Uloom Deoband