You're going to need to create a linked field and link the relevant records together, specifically you'd need to add Record 3 to the linked field of Record 1
You could then add a lookup field to display Record 3's "Followers" value, and then use a formula field to get the difference
How to create that link's slightly trickier. Given that you're familiar with scripting I'd suggest just scripting something as that'd be the easiest option
I guess you mean 194335-194328, considering the time stamps?
You have a linked field with IG accounts, so you have a linked table with a list of them?
You should add rollup field there to get a MAX or MIN value for such IG account. And then return this value back to this table via lookup.
If you cannot rely on MIN/MAX (when the number of followers may increase or decrease), you can rollup the earliest or latest date. Then use it to get the correct value.