Japspeed /Greddy exhaust help

Some more advice please gentlemen!

About to do a manual conversion and due to the exhaust pipe on the new car (the section that bolts on to the turbo) being rotten, I hope to use the pipes off of the old car. Now on the old car I have a japspeed system from the turbos back and on the new car car I have Greddy system from cat back. First question is what is the section that bolts onto the turbo called? I presume it's a decat?

Second question, can I use this section from the japspeed exhaust and the Greddy catback? Do they join with the same flange?

And lastly, the japspeed exhaust has no lambda/O2 sensors, so if I were to use this do I just unplug and remove them?

Thank you.

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