Hello
Is there any way to controll layer 2 connecyivity of a device directly connected to a mikrotik interface? I dont know the mac address and default ip of this device?

No, you can't control what IP it has if its not listening for DHCP, so you could try broadcasting DHCP and see if it picks one up?

You can add an IP in common subnets and do an IP scan to see if it shows (ICMP or ARP)

You can google the device and see if its noted down anywhere its default details.

RouterOS keeps ARP table ... you can check it under /ip arp ... not sure if that table gets populated only when device communicates with router directly or even if it uses RB as a switch. Anyway, ARP table contains interface as well ...

Nice title for the topic "Mikrotik", really explicit...
What laziness...

EDIT: Now is "L2 Connection controll"

An obtuse question begs for vague answers.
What is your real problem stated clearly................. in words without stating any configuration words or the word L2.