Does the direction of a dependency connector matter in UML? -

i have come across several examples of dependencies e.g. include, extend utterly confusing. 1 example dictates include should in direction of;

user profile --> login 

whilst extends should in direction of;

validate credit card <-- print receipt. 

whereas required should in direction of; life of me don't why can't include

place order --> create account 

also matter how these constructed i.e.

user profile --> login (include)        **vs**  validate credit card (extend)        ^        |        |        |   print receipt 

i not sure understand every part of questions, here go:

an include goes including included. denotes mandatory sub part of use case :

including -----------> included           <<include>> 

extend same include, sub part not mandatory. , unfortunately, arrow other way around. seems puzzle lot.

including <----------- optionnally included             <<extend>> 

when speak required, suppose anonymous dashed arrow? in fact, such dependency can written anything, use case or not. not usual use cases, mean use case has prerequisite. difference include is not sub part. in case, drawn way.

requiring -----------> required 

in example, seems place order, must have created account (logical indeed). account creation not sub part of order placing, not include.

as last question, talking vertical/horizontal? if so, not matter in uml. in fact, there no rule positioning, rule remain clear.