The adapter should auto connect hto the phone, when the radio is switched on, as long as it's set as a trusted device (Android, similar but different for IOS).
The commands the radio can send to the phone are limited to those that are supported by the CD Changer, so, not many. Some adapters allow hands free call answering, not much more. Read the spec for each adapter, to see what's supported, but, remember it's 20 year old tech! Get a decent phone mount (OEM Mounts are good), and let your fingers do the necessary.
https://www.oem-mounts.com/
Mac.

 

Thanks for the reply. Yeah, (1) seems likely as most devices do that, (2) I can't find any information on. The product info pages and video reviews never mention the power-on behaviour, or which play/pause/next/previous controls are actually passed through to the phone and acted on. I'm trying to avoid having to tib at the phone each time I get in or start the engine.

Can anyone with one of these devices confirm if it'll auto-play at power on?

 

The radio cannot communicate with apps like Spotify and Poweramp, etc, as it had no suitable command. So, unless you can set a routine on the phone (Google Assistant perhaps) to autoplay when BT connection is established, I don't think you'll win.
You could just say "Hey Google, Play Spotify"...
Mac.

 

Not quite - just passing through the 'play' command would do it, many headphones/etc have that ability and this would be no different, same protocol, AVRCP. Just trying to find someone who has one of these so I can find out if they bothered to implement play-after-connect like some aftermarket stereos do, regardless of which phone or app it is.

The marketing materials for these tools say they support some controls and specifically name AVRCP being supported but that doesn't give enough info and none of the people making videos about theirs take a moment to do this, very superficial stuff, so I'm asking here!