Does the Harbor Freight 9 AMP Chicago Electric Reciprocating Saw (Professional Series) got enough SPM and/or Power to cut through Steel?

You get what you pay for when purchasing tools or most other things. One of the best reciprocating saws on the market is from Milwaukee, another is Bosch. Most of the Made in China tools sold by Harbor Freight are for home and hobby use. For thick steel (+5mm or 1/4") a cutting torch is a better choice. The blade selection will determine the time to cut through anything.

How thick the steel is doesn't matter. How HARD the steel is determines if a given tool will cut it. Thickness only determines how long it will take. Plastic would tend to dull a metal cutting blade more quickly, but the blade would cut through nearly any plastic.

I rather doubt it. I tried one (from HF) many years ago when money was Tight and took it back the next day. Compared to Milwaukee, DeWalt, Bosh, Porter Cable it was garbage. For what you say you want to do I suggest getting the largest motor (Amps) you can find. 12 amps is the highest you will likely find. Couple that with high quality blades and a little cutting oil and you may be OK.

How many blades do you intend to go through. The answer, a reciprocating saw doesn't have the teeth to do that job and would wear out rapidly. Plastic would be no problem. For steel that thick you need a torch.

They will cut thru thin steel. But it's not intended for thick stuff. Use a metal cutting bandsaw.

Two or three inch steel???

You're kidding right?

That tool might nibble through one or two such pieces in it's service life.