请教两个 robots.txt 相关的问题

robots.txt 内容:
User-agent: *
Disallow: /subject_search
Disallow: /amazon_search
Disallow: /search
Disallow: /group/search
Disallow: /event/search
Disallow: /celebrities/search
Disallow: /location/drama/search
Disallow: /forum/
Disallow: /new_subject
Disallow: /service/iframe
Disallow: /j/
Disallow: /link2/
Disallow: /recommend/
Disallow: /doubanapp/card
Disallow: /update/topic/
Disallow: /share/
Allow: /ads.txt
Sitemap: https://www.douban.com/sitemap_index.xml
Sitemap: https://www.douban.com/sitemap_updated_index.xml
# Crawl-delay: 5

User-agent: Wandoujia Spider
Disallow: /

User-agent: Mediapartners-Google
Disallow: /subject_search
Disallow: /amazon_search
Disallow: /search
Disallow: /group/search
Disallow: /event/search
Disallow: /celebrities/search
Disallow: /location/drama/search
Disallow: /j/

1./group/topic 在标注为 Disallow 和 Allow 中都没有出现，那么应该默认为 Allow 还是 Disallow ？
2."# Crawl-delay: 5"的单位是什么？