If I’m understanding it correct, 4.0 had some fundamental differences in terms of code structure, i.e. not everything is downward compatible.

For me 4.0 candidate works just fine to be honest :)

Rule of thumb I learned and never validated:

Two it starts, with three it can become an issue, with four it might affect the underlying permanent teeth - and there is no difference between thumb or pacifier.

4.0 is the next big version that’ll come … Whenever.

VLC has no big corporate sponsor behind them and are notorious for being thorough but slow - i.e. what they released in the past was top notch but it took them six years to go from 2.0 to 3.0.