What will happen if we disable the "AND" element (DD3) in the adder and close the carries of P and C?

Question

Electronics

That's what I think, correct me if I'm wrong. If we turn off the "AND" link and close two transfers, then the adder will perform the simplest addition operations 1+0 or 0+0, giving 1 or 0. We have closed the transfers, which means that most likely at 1 + 1 it will give 0.

Answer 1

By closing the transfer output to the transfer input, you will create a feedback loop)
The adder is a combinatorial element, i.e. the state of its outputs depends only on the state of the inputs.
By introducing a feedback loop, you form a trigger in it, i.e. it will already be a serial device (a device with memory).
Here, see an example in an online simulator consisting of a one-bit adder with such a feedback loop: https://tinyurl.com/ybptoom7 .
Notice how the output changes with and without feedback. In the presence of feedback, the transfer output stores the state of one until both data inputs are zero, but in the absence of it (feedback), the transfer output immediately goes to zero if there is only one unit at the inputs.