Here's Scorpius and Trakeena
Here's the Scorpion Stinger
This shot of the Magna Defender is new footage
This shot is the start of Sentai footage along with this shot
Here's Freaky Tiki in the Scorpion Stinger
Once you see Tiki's feet running on the ground on Terra Venture then that's another start of Sentai footage.
These shots
is when it goes back to new footage.
This shot of the Magna Defender and the Red Ranger is when it goes back to Sentai footage.
Most of the Magna Defender's flashback explaning how he knows Mike is Sentai footage however some new footage is in the flashback - basically just the shots of which you can clearly see that Mike is in the shot.
The shot that you see of the Magna Defender stealing Mike's spirit by switching life forces with him is new footage but it's cleverly edited so that they can seamlessly edit into the Sentai footage once you see the Magna Defender suit materialize over the Mike body.
Once the flashback ends, the Sentai footage continues playing.
There's a commercial break but once the show returns from its break, there's an exterior shot of Terra Venture and then it cuts back into Sentai footage.
The flashback of Magna Defender giving his Dart to Zika is all Sentai footage.
You see Freaky Tiki growing in Sentai footage. You don't see him drink the green liquid in Power Rangers but he does end up drinking his Growth Potion in Sentai.
After Scorpius tells Trakeena to disconnect, it then cuts back to Sentai footage of the Rangers.
The footage on the Megaship Viewing Screen is also Sentai footage.
Obviously once the Rangers are forcibly demorphed, that signals another start of new footage.
Thos shot of the Magna Defender is when it goes back to Sentai footage.
These shots
is when it goes back to new footage.
Those last 2 shots is new footage because they had to reshoot it since that's around the time when the Magna Defender released the lifeless Mike body at in Sentai footage even though in Sentai it would have been Hyuuga.
This shot of the Magna Defender is when it goes back to Sentai footage.
This shot of the Magna Defender is new footage
This shot of the Magna Sword is when it goes back to Sentai footage but only briefly because it then cuts back to the unmorphed Rangers.
It then cuts back to Sentai footage of the Magna Defender.
You see the usual Torozord charging onto the scene entrance which is Sentai stock footage.
The big time difference between the 2 scenes is that the Magna Defender changes into energy while still on the cliff whereas in Sentai, BullBlack jumps off the cliff before he changes into energy.

Sentai footage comes from Ginga Episode 25