I also think 1framing at the very edge will work for the 1st jump you posted and I think the 2nd jump is possible without the platform. For double inverts, though, I wouldn't recommend the bunnyhopping strat if you're bad at 1frames and because you don't know your valign (has to be between y.3-y.5), but you can cactus cancel by pressing 2 left shifts or 2 right shifts fast in midair if you have a good keyboard (I can't do lower jumps than 1frames when I cactus with my keyboard) or you just can cancel in midair (also using 2 left shifts or 2 right shifts).
For last method (which is the one I use and recommend) you need to have a shift holded, press the other one (the kid won't jump here) and when you want to cancel (in midair in this case) tap the other shift fast and release the other one you had holded immediately after. The jump will be lower or higher depending on the time between the 2 shift releases. Oh, and the height you need for that cancel is almost a full cancel height (same as a 1frame).