Some of the recently (September 2023?) introduced changes for Level 4:

Natural opening bids at the 2 level must contain 5+cards; or if only 4 must specify a second suit.

Stayman & transfer bids as responses to 1NT & 2NT are announced, and you also announce “Clubs” or “Diamonds” if a 2S or 2NT response to your 1NT opening is a transfer, showing that suit. But if 2S or 2NT shows both minors, or could be either minor, then the bid is alerted – only announce if the bid shows just one suit. 1NT is announced but 2NT is not alerted.

Strong* artificial 2C & 2D opening bids are announced as are natural two level opening bids
* strong is now defined as 16+ HCP or 13HCP in 2 suits containing 10 cards (except if long suit is clubs).

Doubles of suit bids on first round Alert if for penalties and double of 1NT Alert if Not for penalties. No announcement or alert for bids after the first round. BUT if in doubt alert or announce and if partner makes a bid which you think should be announced or alerted and then if opponents ask respond “we have no agreement”.

Equally doubles below 3NT will be assumed as take out unless announced otherwise.

Opening at two level e.g. 2 hearts or 2 spades then must add “weak”, or “strong NF” or “strong and forcing” or “intermediate”.

For other strong bids (for example, opening 2C or 2D) the requirement is 16 or more HCP, except if there are two suits with 13HCP concentrated in the two suits. S: x; H: xx; D: AKQxxxx; C: Axx is 13HCP contained in two suits total 10 cards. And 2C (strong) can also be use for a hand such as

S: AKQxxxxx; H: xx; D: xx; C: x

this has great playing strength with only 9HCP and importantly the long suit must NOT be clubs