Yes the Apollo 11 astronauts did use the L.E.M or the Lunar Explorer Module.
The name of the LEM (Lunar excursion model) was Aquarius (:
The Apollo 13 crew had to move things around inside the Lunar Module (LEM) and Command Module (CM) to conserve power and oxygen, as the mission faced a critical situation following an oxygen tank explosion. Additionally, transferring items between the two spacecraft allowed them to utilize systems and resources from one module to sustain life in the other.
The Apollo 13 crew used the Lunar Module as a lifeboat after an oxygen tank exploded, damaging the Service Module. They made critical repairs and used the gravitational pull of the Moon to slingshot back towards Earth, re-entering the atmosphere and splashing down safely in the Pacific Ocean.
The LEM Aquarius was the Lunar Module used during the Apollo 13 mission. It was designed to land on the moon but was repurposed to serve as a lifeboat for the astronauts to return safely to Earth after an oxygen tank explosion on their spacecraft. The Aquarius played a critical role in helping the crew survive and ultimately make it back home.
Apollo 3 was a test flight and therefore had no crew.
Jim Lovell's crew was originally scheduled for Apollo 14, but due to medical reasons, the original Apollo 13 crew had to be replaced. Lovell and his crew were then re-assigned to Apollo 13.
Alan Shepard and his crew was supposed to fly Apollo 13, but he got an ear infection close to the launch, so the crew of Apollo 14 were moved up a place allowing Alan Shepard to fly Apollo 14. The reason the whole crew switched was because they trained with each other and were put together to compliment each others skills.
Usually Velcro
Yes they did. By using the Lunar Module (LM or LEM) built to land on the surface of the moon as a lifeboat. The crippled command module and the damaged service module had to be shut down to conserve power and resources for the astrnauts to survive.
carry a crew of two from lunar orbit to the surface and back
The Apollo 1 crew consisted of Gus Grissom, Ed White, and Roger Chaffee
Apollo 4 was a test flight that did not have a crew. It launced November 9, 1967.