UE fallback data loss

Mobility
1

Hello Everyone,
I have a question.
UE has 2G, 3G, 4G and in times they fallback to the lower RAT, how the UE and network manages that?
I mean during call we don’t feel any data loss?
Kindly help if you know.

2

Yes, DATA loss will be der as it is Hard HO.

3

Thanks!
And how that process actually occurs?