Classic RISC pipeline question
In the first part of the question, you are correct that the only data dependencies are from the first instruction to the third instruction and from the second instruction to the third instruction.  You are also correct that there is no data dependency between the first and second instructions.

Similarly in the second part you are correct that there is a data dependence from the first instruction to the second and from the second to the third.

Data forwarding has nothing to do with which instructions have data dependencies.  There is always a data dependency from an instruction that produces a value to any other instructions that consume that value.

Given that there are data dependencies the presence (or lack of) forwarding impacts performance.  But I can't tell you how much stalling you would need because I don't know your pipeline latencies.  Forwarding typically reduces the amount of stalling required.