Here are the precise answers based on the current regulations for Mumbai Airport (BOM).
1. Do you need an Indian visa for a few hours?
The answer depends on a single technical criterion: do you have a single booking reference (PNR) for the entire journey or two separate tickets?
Case A: Single ticket (End-to-end ticket) If your Air India and SriLankan Airlines flights are on the same reservation (same PNR number), you remain in "International Transit."
You do not go through immigration.
You stay in the transit area of Terminal 2.
No Indian visa is required.
Case B: Two separate tickets ("Self-transfer") Even without checked baggage, if these are two distinct bookings, the airline may require you to go through immigration to "enter" the country technically before checking in for your next flight.
In this specific case, a Transit Visa is necessary.
Important: Even if you have no baggage, some airlines may refuse boarding in France if you don’t have an Indian visa for separate tickets, as they cannot guarantee your access to the transit area in Mumbai.
2. Do you need a double-entry visa?
If you are in Case B (separate tickets) and need a visa:
Yes, you absolutely need a "Double Entry" visa. Since you’re making the same trip 26 days later, you’ll "enter" the Indian transit zone a second time.