You should always be able to run local for your current directory version of ANGULAR CLI by running:
node_modules/.bin/ng <ANY NG COMMAND>
instead of just
ng <ANY NG COMMAND>
just make sure, you are running this command from the root directory where your main package.json is located (and its node_modules directory)
There is an npm command returning node_modules/.bin path (which may be used for shorter writing):
// does not work on Windows
`npm bin`/ng <ANY NG COMMAND>
Note that back ticks are used around npm bin and not single quote sign.
ng command is also added to package.json scripts section, so it is also possible to run local copy like this:
npm run ng -- <NG_OPTIONS>
note -- flag terminator, it must be inserted before ng options.
If you want to create a new ng project using particular version but without installing @angular/cli globally, you can use npx command:
npx @angular/cli@7 new <APP_NAME>
here npx will temporary install @angular/cli with latest (@7 at the time of answering :)) version and run its ng executable with passed parameters.
You even can do something completely useless (because local copy of @angular/cli was installed with ng new). Run ng serve with @6 version of CLI on @7 new project:
cd <APP_NAME>
npx @angular/cli@6 serve
UPDATE
Running these commands will use ng executable located locally within node_modules/.bin/, so you do not need to have it installed globally:
cd <APP_NAME>
npx ng serve