I can definitely tell you that any footage of the Dark Trio in the Skull Cavern in this episode is new footage however in regards to this shot of Vypra, Loki and Impus it's possibly Sentai footage but I can't be certain on that. It looks like new footage.
All footage of the Mirror Card is new footage.
Carter gets a message from Captain telling him to go to Rescue Ops and then in the next scene you see the Dark Trio punching a wall, the Dark Trio punching a wall is the start of Sentai footage.
Looks like the footage that's shown on the Rescue Ops' monitor is new footage.
It's hard to tell because Captain Mitchell is blocking the Monitor but the footage that plays on the monitor behind him while he's addressing the Rangers is more than likely Sentai footage.
Once the Rescue Rover begins lowering on its lift, the next scene you see is of the Dark Trio in new footage.
Here's a shot of the 6 Rangers
Here's a shot of Falkar, Demonite, his copy and Thunderon Any shots of ground footage involving Demonite's copy is new footage because there was no ground footage available for his copy in GoGoV because he didn't have a copy in GoGoV. His copy here is actually what Demonite grew into when he ended up growing in GoGoV.
Once you see this shot it's back to Sentai footage. After you see the Titanium Ranger fighting Demonite's copy, the scene switches to this shot which is when the Red Ranger calls for his V-Lancer.
This shot of Falkar appears to be the start of new footage since this shot of Falkar doesn't correspond with any GoGoV footage of Falkar.
Once you see a close-up shot of Thunderon, it's back to Sentai footage once again.
Once you see Titanium Ranger being beaten up by the Demonite copy, the scene changes to a shot of the 5 Rangers which appears to be new footage since the Pink Ranger in GoGoV as far as I recall hasn't been seen communicating like that.
This shot of the Rangers and the Dark Trio is the start of Sentai footage.
Ryan demorphs during his fight with the Demonite clone and then it goes to commercial break. Once it returns from commercial break, it's the start of Sentai footage once again.
This shot of the Red Ranger is the start of new footage however this shot means that it's right back to Sentai footage.
This shot means it's back to new footage however it goes back into Sentai footage once the camera moves around in order to show Thunderon and Falkar at the scene of the battle where Falkar basically tells Red to just go for it because Falkar is sure that Carter is well aware at that close distance he'll blow up himself (Carter) too.
This shot of the Red Ranger means that it's back to new footage once again however once the scene changes, it changes to a Demonite shot which is back to Sentai footage once again.
This shot of the Red Ranger means that it's back to new footage once again however once the scene changes to a shot of Demonite, it's back to Sentai footage once again.
This shot of the 4 Rangers means that it's back to new footage once again.
Once the Demonite clone blows up, as soon as the scene changes, it's back to Sentai footage once again.

These shots    
are new footage so the first shot is the start of another new footage block.
This shot of the 4 Rangers is Sentai footage so this shot means that it's back to Sentai footage once again.
This shot is back to new footage.
This shot is back to Sentai footage once again.
This shot is back to new footage.
This shot means that it's back to Sentai footage.
This shot of the Blue and Green Rangers is new footage so that means this shot is the start of new footage once again.
This shot means that it's back to Sentai footage.
This shot of the Green and Pink Rangers is new footage so this shot is the start of new footage once again. How many times am I going to say that within this page?
This shot of the Red Ranger means that it's back to Sentai footage once again.
They end up using the stock shot of the Lightspeed Megazord with its Saber in its right hand activating its fiery Finisher even though Demonite broke off the right hand during the battle.
This shot is something that I'm unsure of. There's an identical shot like it in GoGoV Episode 20 however there's no civilian in the shot and in the GoGoV Episode 20 shot, the Lightspeed Megazord is without its right arm because of Demonite breaking it off during the fight so I'm unsure if this is new footage or Sentai footage but regardless all other Giant footage is Sentai footage.
According to the fandom however, this shot of the Lightspeed Megazord and Supertrain Megazord as well as the background is Sentai footage however the Lightspeed Megazord's right arm/hand has been edited into the shot along with Ryan being edited into the shot.
This shot of Impus and Diabolico looks to be new footage

Sentai info comes from GoGoV Episode 20