Subnet – Pinging across different subnets? This shouldn’t work but it does

That's the whole point of VLANs. VLANs create a layer-2 separation. You can't get from one layer-2 domain to another without a layer-3 device (router) connecting them. The switch is just another host on a different VLAN.

The VLANs are like yards separated by fences. You need a gate (router) to get from one to the other.

If you add a VLAN 2 SVI on the switch with an address in the same subnet as the PC, you could ping the PC.

Based on you comments, it seems that you first problem is that you don't know how to subnet, and you need to divide your 23.12.0.0/24 network into four subnets. You can do this by using /26 networks.

Assign a different /26 network to each of the sites, and you will need a network different than the site-assigned networks for you router-to-router link. Usually, you will use a /30 or /31 network for a point-to-point link like you have between the routers.

Once you have the networks correctly assigned, you can set up your routing. Each router will inherently know about the networks directly connected to it, but the router will need to be told about the networks on the other side of the other router. You can do this with static routes (this doesn't scale well), or you can run a common routing protocol between the routers that will automatically tell each router about the networks connected to to the other router.