Socket 7
No. The Intel Pentium 4 line was produced for three sockets. The shortlived Socket 423, Socket 478, and LGA 775 (sometimes called Socket T).
No, the Pentium 3 and Pentium 4 are not only samples of 2 completely different architectures, but also use a different socket so a change between the 2 on the same motherboard is impossible.
The Intel Pentium II was released in a Slot 1 package, while the Pentium Pro used socket 8. Adapters were available to use Pentium Pros in Slot 1 motherboards, and a version of the Pentium II was released for Socket 8.The Intel Pentium II includes MMX instructions, while the Pentium Pro does not.The Intel Pentium II has improved performance in 16-bit applications. 32-bit applications were not affected quite as much.
No. It is a higher-end version of the same processor, with a larger amount of L2 cache. It cannot be used as a replacement, since they use different slot / socket types.
It is a CPU, designed for use in socket 7 motherboards. It was designed to be competition to the Intel pentuim/pentuim MMX range of CPUs.
Pentium 4s were available in Socket 423, Socket 478, and LGA 775.
The CPU can be upgraded only if your motherboard/chipset and BIOS support it. Socket 478 motherboards cannot support a Dual-Core, as they use a different socket. If you have an LGA775 motherboard, it may work, but chipsets before 945 are not officially supported and may fail to function properly.
Socket 8
It depends. Pentium 4 processors came right as Intel began to change from what is called Pin Grid Array (the processor has several hundred pins on the bottom) to Land Grid Array (the CPU socket has pins which contact the processor). Older Pentium 4 processors run on PGA Sockets 423 and 478, which are no longer found on mainstream motherboards, but the newer Pentium 4's were built for the LGA 775 socket, which can be found on some new motherboards.
Pentium 4 sockets were sockets numbers Socket 423 for early Pentium 4's. Then socket 478 for Pentium 4, Pentium 4 Extreme Edition and Celeron and socket T (LGA 775) for Pentium 4, Pentium D dual core, Celeron D and Pentium Extreme Edition.
Pentium Pro
Yes.