Is it permissible to design shapes of living beings from cut and assembled paper, and is that considered unlawful and does it prevent angels from entering? And does the same ruling apply to what is made from other materials?

It appears that your brother's act of assembling and designing an animal image from paper is considered among the prohibited three-dimensional images, and it prevents angels from entering homes. The prohibition is indicated by what Al-Bukhari and Muslim narrated from Abdullah ibn Mas'ud - may Allah be pleased with him - who said: The Messenger of Allah, peace and blessings be upon him, said: "The most severely punished people on the Day of Resurrection will be the image-makers." And what Al-Tirmidhi narrated from Ibn Abbas - may Allah be pleased with both of them - who said: The Messenger of Allah, peace and blessings be upon him, said: "Whoever makes an image, Allah will punish him until he breathes life into it - meaning the soul - and he will never breathe life into it. And whoever listens to a conversation of people who dislike his presence, molten lead will be poured into his ears on the Day of Resurrection."

The absence of the two legs does not affect this; permissible images are those that have a defect with which life cannot exist, such as being headless, or without a neck, or without a torso, and so on, where life cannot exist without them. So if the head is cut off or a part without which life cannot remain, it does not fall under the prohibition. However, the loss of limbs after which life can still remain, such as an eye, a hand, or a foot, means it remains under the prohibition.