Safe to always use 之後 instead of 以後, and 之前 instead of 以前? According to this grammar page, it appears like 之後 can always replace 以後, whereas 以後 cannot always replace 之後. However, these grammar pages are not always reliable.

1) For simplicity, is it safe to always use 之後 instead of 以後?

2) Is the same true of 之前 and 以前?

https://resources.allsetlearning.com/chinese/grammar/Comparing_%22yihou%22_and_%22zhihou%22
In the three example sentences of 以后 in your link, 以后 cannot be replaced by 之后.

(1)以后 再 也 不 来 这里 吃饭 了 ， 又 贵 又 难吃 。
(2)以后 我 可能 会 去 国外 上 大学 。
(3)以后 的 事情 以后 再 说 吧 。


(Actually you can use 之后 in (2), but need a context before that. E.g. 我打算高中毕业之后去北京工作两年;之后我可能会去国外上大学。)

Similarly 之前 and 以前 cannot always replace each other.