Deliberate mistake: When the bear pulls Woody into the garbage bin after the other toys have crossed over, his hat is not pulled off when his body is squeezed under the lid when going down. (01:15:35)
Deliberate mistake: Despite being squeeze toys, the Little Green Aliens couldn't possibly have got their feet stuck between the two dumpster lids because both the lids are closed after Big Baby throws Lotso in and the gap between the two dumpsters is far too small for any of the toys to get stuck between. Lotso certainly didn't lift the lid off-screen, we would have heard him do it.
Answer: Yes, he is. He can be seen wearing the same black t-shirt with a skull motif that his younger self wore in the first movie and Pixar have confirmed that the character's intended to be Sid.
Tailkinker ★
In addition, they are voiced by the same person.