Does APB allow multiple beats in a transfer like AXI/AHB?

No, each APB access is a single transfer (read or write).

You can have multi-beat APB sequences, but they will just be a sequence of single APB accesses.

So AXI has AxLEN to indicate how long a transaction will be, and AHB has HBURST to signal some defined length bursts, but when these are converted to APB they will just become an AxLEN or HBURST length long sequence of individual APB accesses, potentially with PSEL remaining high during the sequence, or possibly with PSEL pulsing low between transfers (depending on the design of the APB bridge component).

There is no APB "burst length" signal, so the target peripheral just sees an unrelated series of transfers.

No, each APB access is a single transfer (read or write).

You can have multi-beat APB sequences, but they will just be a sequence of single APB accesses.

So AXI has AxLEN to indicate how long a transaction will be, and AHB has HBURST to signal some defined length bursts, but when these are converted to APB they will just become an AxLEN or HBURST length long sequence of individual APB accesses, potentially with PSEL remaining high during the sequence, or possibly with PSEL pulsing low between transfers (depending on the design of the APB bridge component).

There is no APB "burst length" signal, so the target peripheral just sees an unrelated series of transfers.